<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../vue.js"></script>
</head>

<body>
    <div id="app">
        <input type="text" v-model="msg"/>
        <button @click="num++">累加</button>
        <h1>doubleNum: {{doubleNum}}</h1>
    </div>
    <script>
        Vue.config.productionTip = false;
        
        const vm = new Vue({
            el: "#app",
            data() {
                return {
                    msg: "",
                    num: 1
                }
            },
            computed: {
                doubleNum() {
                    return this.num*2;
                }
            },
            /* wacth可以监听一个data属性或者一个计算属性,就会触发watch侦听的回调函数,我们可以在回调函数中做后续的事情 */
            watch: {
                msg() {
                    // console.log(this.msg)
                    console.log('发请求');
                }
            }
        })
</script>
</body>

</html>